Republicans and gun owners started turning against him after he rammed through the nation’s first post-Newtown gun-control law, a new poll found.

Democrat Cuomo’s approval rating slid from 74-13 percent last month to 59-28 in the Quinnipiac University poll released yesterday, a 30-point differential swing.

The news came a day after the New York affiliate of the National Rifle Association filed an intent to sue to stop enforcement of the law, arguing it unconstitutionally deprives New Yorkers of their rights.

While voters in nongun homes gave Cuomo a whopping 68-19 thumbs-up, those households with guns turned against him by 50-40, the Jan. 23-28 telephone survey of 1,127 state voters found.

His standing remained high in the city and suburbs, but not so in upstate and in rural areas.

White voters and men aren’t as high on him as are black voters and women, the poll found.

“They’re afraid you’re talking about taking their guns away,” Cuomo said of gun owners. The law, though, “has nothing to do with the legitimate ownership of a gun,” he insisted.

“It has to do with keeping guns out of the hands of people who are mentally ill, keeping guns out of the hands of criminals, and cracking down on illegal guns.”

The poll found that 34 percent of voters said Cuomo’s law goes “too far” in restricting gun owners’ rights, 30 percent said it doesn’t go far enough in protecting public safety; and another 30 percent called it “about right.”

Meanwhile, at an emotional hearing in Newtown last night, parents of several victims of the massacre urged legislators to tighten gun laws.

“Turn this tragedy into a moment of transformation,” said Nicole Hockley, whose 6-year-old son, Dylan, was killed in the massacre.

In a further effort to heal, 26 students from the chorus at the Sandy Hook Elementary School are scheduled to sing “America the Beautiful” in the pregame show before the Super Bowl between the San Francisco 49ers and the Baltimore Ravens Sunday.